Mammography is the current cost-effective gold standard for breast cancer screening. However, its usefulness has recently become a subject of considerable debate. The limitations of mammography are most evident in the population of women who have dense breast tissue where up to half the cancers can be missed. Furthermore, mammography generates radiation and can be quite uncomfortable. While magnetic resonance imaging (MRI) can be more accurate than mammography, it is not practical because it is too expensive for routine use. Currently, there is a trade-off between the cost effectiveness of mammography on the one hand and the imaging accuracy of MRI on the other. This trade-off represents a barrier to increasing survival rates for women who develop breast cancer. Our long-term goal is to eliminate this trade-off and thereby improve breast cancer survival rates through the introduction of safe, cost-effective, operator-independent sonography based on the principles of ultrasound tomography (UST). The objective of this study, and the next step in pursuit of that goal, is to demonstrate that our new UST scanner is ready to become a clinical and commercial product. The study is justified by the fact that our prior work has already demonstrated the feasibility of breast imaging with UST while the new design promises to greatly increase the performance of the scatter. By demonstrating the improved performance we will be able to introduce a practical, low-cost product for breast cancer screening and diagnosis with potential for significant societal impact. We propose to test the SoftVue system in the lab (Phase I) and then in the clinic (Phase II) to determine its performance and readiness for the marketplace. This study is expected to generate supportive evidence for regulatory clearance and important input for planning large scale screening trials so that the company can undertake its Phase III activities of (i) selling SoftVue scanners for the diagnostic marketplace and (ii) undertaking screening trials to support future regulatory approval for screening.